Organic.inorganic perovskites are promising
materials for improving the efficiency of solar cells, but there
are still uncovered issues on the understanding of their
electronic band structures. Using first-principles calculations,
we investigate the electronic band features of organo-lead
iodide perovskites and present the efficient model to predict
the band gap variation based on the orbital interaction scheme.
The orbital interaction between Pb and I atoms can be
controlled through the structural modification such as the
change in lattice constant and the deviation of I atoms from
cubic symmetry sites. The increase of the lattice constant and
the positional distortion of I atoms from the cubic symmetry
sites lead to the increase of the band gap. With our findings,
puzzling band gap variation behaviors in previous experiments and simulations can be understood, and we suggest a pathway to
precisely control their band gap. Our study can serve as the design rule for band gap engineering for various kinds of organic.
inorganic hybrid perovskites.